White LED (Light Emitting Diode) has some advantages such as small power consumption, long usage life, environment protection and so on. With the improvement of the luminous efficiency and lowering of the production costs, the white LED is expected to become a new generation of lighting source following the incandescent, the fluorescent lamps, and the high-strength gas discharge lamp. The replacement of white LED solid-state light sources to traditional vacuum light is a breakthrough technology innovation as the replacement of the transistors to the traditional vacuum tube, which may lead to a revolution of the lighting field.
Nowadays, the most commonly method to implement white LED is to combine blue LED chip and blu-ray effectively stimulated yellow phosphor. YAG type phosphors is the most mature yellow phosphor, which is an yttrium aluminum garnet (Y3Al5O12:Ce) activated by trivalent cerium ions and can be combined with blue LED chip to form the white LED. Although a relative high luminous efficiency may be achieved, white LED with warm white and high color rendering properties is hardly obtained, due to the lack of red in its emission wavelength. Besides, during the preparation of the YAG type phosphor, a high temperature requires, thus increasing the cost and lowing the luminous intensity. However, as for the non-YAG type phosphor, the biggest problem is the low luminous efficiency.